It belongs to family of dinosaurs known as carcharodontosaurs, best known for their shark-like teeth. Named Ulughbegsaurus uzbekistanensis, it was at least 22 feet (seven meters) long and weighed more than a ton (1,000 kilograms) and would have roamed Central Asia about 90 million years ago.
The jawbone fossil was thought have been unearthed in the 1980s and found its way to the State Geological Museum in Tashkent, Uzbekistan but its significance wasn’t recognized until 2019, said Darla Zelenitsky, an associate professor of dinosaur paleobiology at the University of Calgary in Canada.
The researchers from Canada, Japan and Uzbekistan named the new genus and species Ulughbegsaurus (oo-LOOG-bek-SAW-rus) uzbekistanensis, after the 15th century mathematician and astronomer Ulugh Beg.
“More than 90 million years ago, apex predators of Asian and North American ecosystems were often large species of carcharodontosaurs known as shark-toothed dinosaurs, which were later replaced by large tyrannosaur species, akin to T. rex, sometime around 80 (million) to 90 million years ago,” said Zelenitsky in a statement.
“Both of these groups of dinosaurs were meat-eaters that had sharp teeth and walked on two legs, although tyrannosaurs, in general, were more heavily built.”
How tyrannosaurs evolved to replace carcharodontosaurs at the top of the food chain in these regions isn’t well understood because of a patchy fossil record for the early part of the Late Cretaceous some 80 to 100 million years ago. Apex predators are usually fewer in number than the animals they prey upon, which could explain why their fossil remains are more difficult to find in some ancient ecosystems, Zelenitsky explained.
Zelenitzky said Ulughbegsaurus would have shared the ecosystem with a small species of tyrannosaur called Timurlengia.
“Evidence all told, suggests that the carcharodontosaur species were outsizing or “keeping down” the tyrannosaur species in ecosystems of Asia and likely North America still just prior to their extinction about 90 million years ago,” Zelenitsky said in an email.
The extinction of carcharodontosaurs allowed tyrannosaur species to take over the apex predator role in Asia and North America 80 million to 90 million years ago. They persisted in large forms like T. rex until a massive asteroid hit the Earth around 66 million years ago, dooming most dinosaurs to extinction.